Power amplifier

Abstract

A power amplifier circuit including a low power output general purpose operational amplifier. The circuit provides an output voltage swing far greater in magnitude than the output voltage swing of the operational amplifier and with a faster response than the slew rate of the operational amplifier. The circuit, which is complementary, includes voltage dividers which couple the output of the operational amplifier to constant current mode driver transistors. Power transistors amplify the output of the constant current mode transistors to provide a high power low distortion output.

What is claimed is: 
     
       1. In an amplifier circuit including a conventional operational amplifier and a pair of conventional voltage regulators for providing positive and negative supply voltage to the operational amplifier, the improvement of a complementary circuit for providing low distortion high power class A-B amplification comprising: a pair of voltage dividers, each voltage divider coupled between the output of one voltage regulator and the output of the operational amplifier;   a pair of divider circuits, each responsive to one of said voltage divider networks, each driver circuit operating in the constant current mode and having current flow responsive to changes in the output of the operational amplifier; said pair of driver circuits being connected together at a first terminal;   a pair of power transistors, each coupled to one of said driver circuits; each power transistor operating to prevent junction breakdown and for amplifying the output of its driver circuit;   said pair of power transistors having their collectors tied together at a second terminal and providing the circuit output at said second terminal; and   a feedback circuit coupled between said first terminal and said second terminal to prevent oscillation of the circuit output and to provide negative feedback to said driver circuits, thereby preventing faster response to the output of said operational amplifier.   
     
     
       2. The invention as defined in claim 1, wherein each of said power transistors circuits includes a bias network to maintain the power transistor in conduction. 
     
     
       3. The invention as defined in claim 1, wherein said driver circuit includes a driver transistor operated as a constant current source and having its collector connected to the base of the transistor in said power transistor circuit.